There have been 13 homicides so far this year. By this time last year, there were already 20 dead. And the murder rate is way down from, say, 1986, when 79 people were killed within the city limits.

But cold statistics don't mean much right now to the folks who are in the business of investigating deaths. Not with four bodies on the city's books in the past week, including one of their own.

"We just kind of look at each other at the scenes going, 'Holy cow,' " Tampa police Maj. George McNamara said Friday. "Is it a full moon?"

He's at a loss to explain.

"I've been here for 28 years," he said, "and I've never been involved in a week like this."

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The violence kicked off at 2:26 p.m. on Aug. 15, a Saturday.

A call came in about a potential homicide. The first two officers to respond had just begun their shift at 2 p.m.

Within hours, police would find three people dead at two different homes in an apparent murder-suicide.

"That's one heck of a way to start your shift," said Lt. Brian Dugan, who worked as scene commander that day.

Police consider the first 72 hours after a murder the most vital for a homicide investigation. All 10 detectives on the homicide squad worked the case.

It didn't get their undivided attention for long.

Tuesday, a man walked into a church and said he'd done something very bad. Police officers found the man's girlfriend stabbed to death inside her Sulphur Springs home and charged him with second-degree murder.

Wednesday, a University of Tampa student-athlete, Ryan McCall, 21, was shot and killed on the N Boulevard bridge as he walked home from a bar at 3 a.m. The shooter had demanded money.

Nineteen hours later, Cpl. Mike Roberts was gunned down after he questioned a man about why he was pushing a full shopping cart down N Nebraska Avenue.

Four murders. Five days. (One of the victims in the murder-suicide was found dead at his home outside the city, so that death is considered part of the county's homicide rate.)

All the cases needed to be worked simultaneously and with urgency.

The student's killer remains on the loose. Police quickly arrested the man they believed killed Roberts, but they had few clues about his motive.

Detectives told their spouses and children not to expect them home any time soon. They had evidence to collect, interviews to conduct, grieving families to console.

Hard as it was to investigate the death of a fellow law enforcement officer, they didn't have time to mourn, McNamara said.

"You just have to be completely, 110 percent focused on your task," he said. "You have to keep your emotions in check."

Nine homicide detectives worked through the night at the scene of the officer's slaying. Capt. Paul Driscoll picked up some water and Gatorade for members of the squad. They were too busy to eat.

Two of the detectives had been out since early Wednesday following leads in the student's killing. Supervisors held back one member of the squad so she would be fresh to attend the officer's autopsy Thursday morning.

When the squad met at 4:30 p.m. Thursday to discuss the progress on the cases, some detectives had been awake for more than 30 hours, McNamara said. By then, most were drinking coffee or Coke.

Everyone was tired. No one complained.

"They want to solve crimes," Driscoll said, ranking homicide detectives among the department's most dedicated investigators. "They want to ensure investigations are thorough and complete and that we can prosecute these cases successfully."

The commitment isn't surprising, said Dugan, who was supposed to be off work Friday but helped field media calls instead.

"That's kind of what cops do," he said.

Yes, they feel sorrow about the lives' lost. Maybe some bitterness, too, he said.

But "we're going to show up and do our jobs," he said. "We're a resilient group."

Colleen Jenkins can be reached at cjenkins@sptimes.com or (813) 226-3337.